Instagram/Mary Cosby & Robert Cosby Celebrity Son of RHOSLC's Mary Cosby, Robert Cosby Jr., dies at 23. A death investigation followed a possible overdose call. Mary shares a heartbreaking statement. March 8, 2026 AceShowbiz - Robert Cosby Jr., son of Mary Cosby from "The Real Housewives of Salt Lake City," has tragically passed away at age 23. According to TMZ, his death occurred Monday evening after police responded to a call concerning a possible overdose, which then led to a death investigation. The official cause of death has not been disclosed.